1. Field of the Invention
This invention relates to a removable press printing module and is especially adapted for increasing the color capabilities of an existing, multi-color press.
2. Description of the Prior Art
Multi-color web printing presses, and particularly multi-color flexographic presses, rotary letter presses, and gravure presses have a large, central impression cylinder with a number of printing units positioned around the periphery of the impression cylinder. As the web is guided for movement around the impression cylinder, areas of the web sequentially come into contact with the plate cylinders associated with each printing unit. Each plate cylinder is supplied with ink of a color different than the color of ink supplied to the remaining plate cylinders so that the desired, multi-colored composite image is formed as the web continues its path of travel around the impression cylinder.
Other types of multi-color web printing presses are constructed with an inline format wherein a number of printing units or stations along with a number of impression cylinders are arranged along a straight line. Each printing station cooperates with a corresponding impression cylinder to form the multi-color image on the web. Typically, the web travels over each impression cylinder and then downwardly along a path around idler rollers before returning in an upwardly direction to the next impression cylinder in order to provide room for drying of each image before the latter reaches the next printing station.
The flexographic, rotary letter press and gravure processes are well suited for printing large areas of solid, brillant colors, and as such are used extensively in the printing of labels as well as many types of packaging materials. In conventional presses of this type, die cutting units removably mounted in slots of the press frame are positioned downstream of the impression cylinder for cutting or forming the web as needed before delivery to the end user.
In general, most common small flexographic presses have three printing units so that a three color image can be produced on the web. However, it is often desired, especially for labels, that images of four or more colors be provided in order to increase the attractiveness of the labels and enhance consumer appeal.
Those printers with inline presses, whether flexographic, rotary letter press or gravure utilizing up to six or more color stations are often faced with the need to add even more colors or a varnish coat to meet customer requirements. In some cases, it may be desirable to mix processes on a particular job for reasons of quality or ease of production. For example, it is generally accepted that varnish is easier to apply flexographically than by rotary letter press. It might, therefore, be advantageous to add a flexographic print station after all the letter press stations have printed.
While add-on printing stations for multi-color presses have been utilized in the past, as a general rule such add-on units are somewhat difficult to install and remove as needed. In this regard, it is sometimes necessary to frequently change the travel of the web and particularly the die cutting units to produce, for a limited time, labels and other printed objects of a particular configuration.